Carburetor



J. M. BARR Dec. 9, 1947.

CARBURETOR Filed Oct. 21, 1944 5 Sheets-Sheet 1 202m Oh HIP-.82

INVENTOR .JZTHNM 17m AGENT .22 20cm Juan J. M. BARR Dec. 9, w 1947.

CARBURETOR Filed Oct. 21,-1944 5 Sheets-Sheet 2 FUEL AIR RAT/u IN ENTCR .jb mr M BARE AGENT Dec, 9, 1947. J. M. BARR CARBURETQR Filed Oct. 21. 1944 5 Sheets-Sheet 4 FIG.

FIG. [4

////////////////////l/l/l/ll ass AGENT Patented Dec; 9,1947.

UNITED srAra CARBURETOR John M. Barr, Meriden, Conn., asslgnor, by mesne assignments, to Niiee-Bement-Pond Company,

West Hartford, Conn.,

Jersey a corporation of New Application October 21, 1844, Serial No. 559,766 14 Claims. (Cl. 281-41) The present invention relates to carburetors for internal combustion engines. and particularly to means for controlling the fuel-to-air ratio in such carburetors. i

Modern carburetors for use on aircraft engines are usually provided with'a manual control device whereby the pilot or some other member of the aircraft crew may select either a rich or lean fuel-to-air ratio. The usual practice is for the pilot to select a rich fuel-toeair ratio under. conditions of high. power output, such as take-off or combat conditions, and to select the lean fuel-toair ratio under normal flight conditions in order to conserve the supply of fuel. The rich fuel-toair ratio is also selected under adverse engine cooling conditions, since an engine runs cooler with a rich mixture than with a lean mixture.

It is desirable under maximum power output conditions to use a predetermined fuel-to-air ratio which is the best under those conditions, and to use that ratio regardless of the position in which the manual control is placed. It is, therefore, desirable to provide some means which sets the fuel-to-air ratio at a predetermined value at maximum power output.

It is customary to provide means for enriching the mixture of fuel and air when the load on the engine exceeds a predetermined value, regardless of the position in which the manual control is set. It has been suggested, in the co-pending application of Scott F. Hunt, Serial No. 498,151, filed August 11, 1943, to provide means whereby the enrichment of the fuel and air mixture takes place at different values of engine load when the manual mixture control is in its different positions.

It is therefore an object of the present invention to provide a carburetor including a manual control by which a lean fuel-to-air ratio or a rich fuel-to-air ratio may be selected, and improved means which operates when the load on the engine exceeds a predetermined value to provide a definite predetermined fuel-to-air ratio regardless of the position of the manual control.

Another object of this invention is to provide an improved mixture control device 01 the type shown in the co-pending application of Scott F. Hunt, previously referred to.

Another object of the invention is to provide a carburetor including a manual control for selecting a lean or rich fuei-to-air ratio, an enrichment control for increasing the fuel-to-air ratio at a predetermined value of engine load, and improved means for causing the enrichment control to operate at different values of engine load when the manual control is in its different positions.

A further object of the present invention is to provide a carburetor including manual control selectively movable to positions corresponding to lean and rich fuel-to-air ratios, enrichment control means for increasing the fuel-to-air ratio at different predetermined values of engine load depending upon the position or the manual control, and means for establishing a predetermined value for the fuel-to-air ratio at maximum engine load regardless of the position of the manual control.

Other objects andadvantages of the present invention will becomeapparent from a consideration of the appended specification. claims and drawing, in which Figure 1 illustrates, somewhat diagrammatically, a carburetor for an aircraft type internal combustion engine including a mixture control and jet system built in accordance with the principles of my invention,

Figures 2 and 3 illustrate two different positions of a mixture control valve mechanism used in the carburetor of Figure 1,

Figure 4 is a graphical illustration of fuel-toair ratio characteristics which are obtainable with the carburetor of Figure 1,

Figure 5 illustrates a modified form of let system which may be used with the carburetor of Figure 1,

Figure 6 illustrates graphically certain fuel-toair ratio characteristics which may be obtained by the use of the jet system of Figure 5,

, mixture control valve mechanisms. and jet sysvtems which may be used in place of the corresponding elements of Figure 1.

Figure 1 Referring to the drawing, there is shown a body ID of a carburetor for an internal combustion engine of an aircraft. Air enters the carburetor body III at an inlet l2 and flows thrua Venturi restriction I4 and a passage I5, past a throttle l6 and a fuel discharge nozzle l8 to an outlet 20. A supercharger may be provided between the outlet 20 and the intake manifold of' the engine. In certain'cases the supercharger may be upstream from theinlet II, or two superchargers may be used, one in each place.

The Venturi restriction It produces a pressure differential between the inlet l2 and the throat of the restriction which varies substantially in accordance with the square of the velocity of the air passing thru the restriction. Since the crosssectional area of the venturi is constant, this unit time. I

In order to obtain a pressure differential varying as a function of the mass of air per unit time flowing thru the venturi I4, the pressure differential between entrance I2 and the throat of venturi I4 is utilized to create an air flow thru a secondary air passage extending from entrance I2 to the throat of venturi M. A plurality of impact tubes 22 are provided, whose open ends project-into the entrance I2 to receive the impact of the entering air. The secondary air passage may be traced from entrance I2, thru tubes 22, a passage 24 interconnecting the impact tubes, a conduit 26, a chamber 28 in a pressure meter generally indicated at 36, a restriction 32, a chamber 34 in the fuel meter 36, a conduit 36, past a valve 38 into a chamber 46, and thence thru a conduit 42 to the throat of venturi I4. I

The valve 38 is operated by a sealed bellows 44 mounted in the chamber 46. The bellows 44 is fixed at one end, so that the position of the free end, to which valve 38 is attached, varies in accordance with the air pressure in the chamber 46. The bellows 44 is preferably filled with nitrogen or some other suitable temperature responsive fluid, so that the position of valve 38 varies not only with the pressure but with the temperature of the air in the chamber 46, and hence with the density of that air.

In the secondary air passage, the pressure differential between the entrance I2 and the throat of venture I4 is divided into two component pressure drops, one across the restriction 32 and the other across the valve 38. The valve 38 is positioned in accordance with the density of the air flowing thru the passage I5. Valve 38 is moved toward open position as the air density increases and toward closed position as the air density decreases. If the volume of air flowing per unit time thru passage I remains constant while its density decreases, then the mass of air is decreased, but the pressure differential set up by the venturi I4 remains constant. However, the movement of valve 38 toward closed position causes the component pressure drop across valve '38 to increase, and the component pressure drop across restriction 32 to decrease, reflecting the decrease in the mass of air flowing. By proper design of valve 38, the pressure drop across restriction 32 may be made to vary substantially in accordance with the mass of air flowing thru passage I5.

This pressure differential across restriction 32 acts on a diaphragm 46 which separates the chambers 28 and 34. The force applied to diaphragm 46 is transmitted to a valve 52, on which it acts in an opening direction.

The fuel enters the carburetor from a fuel pump or other source of fuel under superatmospheric pressure. It flows thru a conduit 56, a valve 52 in the fuel meter 36, a chamber 82, aconduit 56, a mixture control valve mechanism generally indicated at 58, a jet system 66, an idle valve I25, a conduit 62, a valve 64 in a pressure regulator 66, and a conduit 68 to the fuel discharge nozzle I8.

The fuel meter 36 includes a diaphragm 86 separating chamber 34-from chamber 82 and a diaphragm '88 separating chamber 28 from a, chamber 96. A spring 92 biases the valve 52 toward open position.

The chamber 96 is connected thru a conduit 94 to the fuel conduit 62 downstream from the jet system 66. The pressure in chamber 82 is the same as that in the fuel line upstream from the jet system. For any given constant crosssectional area of the fuel passages thru the jet system 66, the pressure differential across it is a measure of the fuel flow thru it. This pressure differential is applied thru diaphragms 86 and 88 of the fuel meter 36 to the valve 62, on which it acts in a closing direction.

From the foregoing, it may be seen that the valve 52 is positioned in accordance with the balance between two forces, one of which varies in accordance with the mass of air entering the carburetor, and the other in accordance with the mass of fuel entering the carburetor. The valve 52 controls the pressure on the upstream side of the yet system 66. 'The pressure on the downstream side of the jet system is maintained substantially constant by the regulator 66, and therefore it may be stated that the valve 52 controls the pressure differential across the jet system. The valve 52 controls the pressure differential across the jet system in a manner to balance the fuel pressure differential against the air pressure differential acting on diaphragm 46.

If the air and fuel pressure differentials are not balanced, the valve 52 is moved in a direction to restore a condition of balance.

The pressure regulator 66 includes a pair of expansible chambers 96 and 98 separated by a flexible diaphragm I66, which is attached at its center to the valve 64. A spring I62 biases the valve 64 toward closed position. The chamber 96 is connected thru a conduit I64 to the conduit 26 and thence thru the passage 24 and impact tubes 22 to the air entrance I2. The chamber 98 is connected to the conduit 62.

The mixture control valve mechanism 58 includes a disc valve I66 fixed on a shaft I68. The valve I66 controls the flow of fuel thru ports opening into conduits II6, III and H2, which lead into the jet system 66. When the valve I66 is in the position shown in Figure 1, fuel can flow thru both the conduits H6 and H2.

- This is known as the "rich position of the mixture control valve mechanism. When the valve I66 is in the position shown in Figure 2, the fuel can flow thru conduits H6 and III. This is known as the lean" position of the valve mechanism 58. When the valve I66 is in the position shown in Figure 3, fuel cannot flow thru any of the conduits. This is known as the "cut-ofi" position of the mixture control valve mechanism 58.

The conduit I I6 conducts the fuel either thru a flXed restriction orjet H4, or thru a restriction H6 controlled by an enrichment valve II8 biased to closed position by a spring I26. The conduit II2 conducts fuel to a fixed restriction I22. Fuel flowing thru the restrictions II 6 and I22 also flows thru another restriction I24.

Fuel flowing thru the conduit III passes thru a restriction I36 controlled by an enrichment valve I32 which is biased to closed position by a spring I34.

Operation of Figure 1 As previously pointed out, the fuel meter 36 controls the fuel pressure differential across the mixture control 58 and the jet system 66 in proportion to the rate of flow of air thru the air passage I5. When the valve mechanism 58 is in l the position illustrated in Figure 2, the only restrictions in the jet system thru which the fuel may flow are the restrictions H4, H6 and I36.

Of these, the restrictions H6 and I 36 are closed by the valves II8 and I 32, respectively. Under these conditions, the variation of the fuel-to-air ratio with changes in air flow is that illustrated by the curve A in Figure 4. At intermediate values of air flow, the fuel-to-air ratio is substantially constant, since the only restriction open to the flow of fuel is the fixed restriction II. When the air flow exceeds a value indicated by the abscissa B in Figure 4, the fuel pressure differential increases to a point where it overcomes the spring I26 and opens valve H6. The opening of valve H8 steadily increases as the air flow increases beyond this value, resulting in a variation of the fuel-to-air ratio as indicated between the, points C and D in Figure 4. When the air flow reaches a value equivalent to the abscissa at point D, the fuel pressure differential becomes large enough to overcome spring I34 and open valve I32. The fuel-to-air ratio then follows the curve illustrated between the points D and E of Figure 4. The point E corresponds to maximum power output, or take-off conditions.

When the mixture control valve mechanism 53 is in the position illustrated in Figure 1,"the fuelto-air ratio varies with the air flow as illustrated by the characteristic F in Figure 4. At intermediate values of air flow, both the fixed restrictions H4 and I22 are open. so that the constant value of the fuel-to-air ratio is greater than that.

obtained when only the restriction H4 is open. When the air flow reaches the value indicated by abscissa B, the pressure drop across the valve H8 is slightly less than the total fuel pressure differential, due to the pressure drop thru restriction I24, Therefore, the valve I'IB does not open until the air flow reaches a slightly higher value, as indicated at G. After valve II8 opens, the fuel-to-air ratio then increases along the curve illustrated between the points G and E. The restriction I24 is provided to limit the maximum rate of fuel flow which may take place thru the restrictions H6 and I22, when both are open. The restriction I24 is larger than either of the restrictions H6 and I22 alone, and, therefore, has little or no limiting action when only one of those two restrictions is open. When both are open, however, it tends to limit the maximum flow. and causes the flattening out observed near the right end of the curve between the points G and E of Figure 4.

At low air flows, such as are encountered under idling conditions, the pressure differential set up by the venturi I4 tends to be erratic, and is not a reliable indication of the air flow. Provision is made to control the fuel flow in accordance with the throttle position at such times. The spring 92 in fuel meter 36 acts on the valve 52 in an opening direction. When the differential pressure acting on diaphragm I6 is small, as under low air flow conditions, the spring 92. becomes the predominating force acting on valve 52. The valve 52, therefore, tends to open, increasing the pressure differential across the jet system beyond that which would be produced if the fuel pressure differential, were maintained proportional to the air flow.

The idle valve I25 is pivotally attached to a lever I26,'whose opposite end is connected by a link I21 to an arm I28 fixed on the shaft I29 of throttle I6. The idle valve is normally wide open when the throttle is beyond the idling range of positions, near its closed position. As the throttle moves into the idling range, the idle valve I25 moves toward closed p sition. At the same time, the spring 92 produces an opening movement of valve 52. The valve 52 is opened sumciently so that its restrictive effect on the fuel flow is less than that of the idle valve I25. Therefore, the

fuel flow under idling conditions is controlled fuei-to-air ratio illustrated at the left end of the curves A and F in Figure 4.

Figure 5 There is illustrated in Figure 5 in modified form a jet system generally indicated at I66, which may be used in place of the jet system 63 of Figure 1. In Figure 5, the parts of the system which are the same as the corresponding parts of Figure 1 have been given the same reference characters. Generally speaking, the restrictions fed by the conduits H6 and III are thesame as the corresponding restrictions in passages of Figure 1. The restriction I22, however, has in parallel with it a restriction I62 controlled by an enrichment valve I64 biased to closed position by a spring I61. The restrictions I22 and I62 deliver fuel into a chamber I66 which is connected thru a valve I68 and a conduit I16 to a jet system outlet conduit I12. The valve I68 is of a rotatable cylindrical type, and is movable to a position wherein the fuel discharged from chamber I66 passes thru the restriction I24instead of passing thru conduit I16 to the conduit I12.

When the valve I68 is in the position shown in full lines in the drawing. the fuel-to-air ratio characteristics obtained are those illustrated in Figure 6. The curve H in Figure 5 illustrates the characteristic obtained when the mixture control valve mechanism is in its lea position, as illustrated in Figure 2. Only the conduits H6 and III are then open to the flow of fuel. It should be noted that the curve H of Figure 5 is generally similar to the curve A of Figure 4. The various elements cooperate in the same way to produce the curve H of Figure 6 as they did to produce the curve A of Figure 4, and it is believed that further discussion of this particular characteristic is unnecessary.

When the mixture control valve mechanism 56 is moved to the position illustrated in Figure 1, however,'the fuel-to-air-ratio characteristic follows the curve J of Figure 6. It should be noted that the curve J starts to rise at an abscissa L, which is substantially to the left of the abscissa K where the curve H starts to rise. This difference is caused by the design of spring 161, which is weaker than spring I26, and therefore allows its associated valve to open at a lower fuel pressure diiferential than that at which valve H8 opens.

When the valve I68 is rotated to the position illustrated'in dotted lines in the drawing, the characteristics obtained are the same as those illustrated in I56, except that the curve'J flattens out more quickly at its right end.

Figures 7 and 8 There is illustrated in Figure 7 a mixture control valve mechanism I15, which may be used in place of the mixture control valve mechanism 58 cludes a disc valve I16 fixed on a rotatable shaft I18. The valve I16 controls the flow of fuel from aconduit 56, which may be the conduit 56 of restriction I98 in series with a variable restric-- tion I92. The restriction I92 is controlled by a valve I94 which is moved in an opening direction by the pressure drop across the valve, and biased to closed position by .a spring I98. The valve E94 is provided with a small fixed orifice I 98, which is not closed when the valve I94 rests on its seat.

Fuel entering the jet system 288 thru passage I82 passes thru a fixed restriction 282 into the chamber WI.

The fuel-to-air ratio characteristics obtained with the jet system of Figure 8 are illustrated in Figure 8A. When the valve mechanism I15 is in its lean position, the fuel-to-air ratio follows the curve M, When the valve mechanism I15 is in its rich position, the iuel-to-air ratio follows the curve N. The valve I94 is an enrichment valve, and it will be noted from a comparison of curves M and N of Figure 8A that valve I94 opens at a higher air-.fiow indicated by the abscissa 284 when the valve mechanism I15 is in its lean position, and at lower value of air flow indicated by the abscissa 286 when the valve mechanism I15 isin its rich position. The difference between these two abscissas is determined by the design of the restrictions I98 and 282.

When the mixture control is in its lean position, the total fuel pressure difierential across thI jet system is applied across the restrictions I9i and I98 in series. The total fuel pressure differential may be considered as being separated into two component pressure drops, one across restriction I98 and the other across restriction I98. The relative magnitudes of these two pressure drops are in inverse proportion to the crosssectional areas of the two restrictions. The pressure drop' across restriction I98 is some predetermined proportion of the total fuel pressure differential. The valve I94 opens when the total fuel pressure differential increases to a point where this proportion is great enough to overcome spring I86.

When both inlet passages I88 and I82 are open, the pressure in the chamber I9I- is increased, since it is now connected to the upstream side of the jet system thru the two parallel restrictions I88 and 282. Therefore, the pressure drop across valve I92 is now a greater proportion of the total fuel pressure differential than it was when the fuel inlet passage I82 was closed. Consequently, the pressure drop across restriction I98 now becomes sufficient to overcome spring I98 at a lower value of total fuel pressure differential than-was the case under the previous conditions. r v

' Fz'gure 9 There is illustrated in Figure 9 a jetsystem 2I8, by which the same fuel-to-air ratio characteristics may be obtained as thoseobtained by the jet system 288 of Figure 8. In Figure 9, the fixed restrictions I86 and 282 are the same as the corresponding restrictions of Figure 8. The variable restriction I92 of Figure 8 is replaced by a fixed restriction 2I2, and the fixed restriction I98 of Figure 8 is replaced by a variable restriction 2I4 controlled by a valve H6. The valve 2I8 is attached to a stem 2-I8 whose upper end is attached to a piston 228, A spring 222 above the piston 228 biases the valve 2I6 to closed position. The chamber on the upper side of piston 228 is connected thru a passage 224 to the outlet of the jet system.

The total fuel pressure differential across the jet system acts in a valve opening direction on the piston 228, and is opposed by the spring 222 and by the pressure drop across valve 2I8 acting on the area of that valve, which is smaller than the area of piston 228. When the inlet passage I82 is closed, the pressure drop across valve 2W, when closed, is the same as the total fuelpressure differential, because thereis no flow, and hence no pressure drop, thru restriction 2I2. Therefore, when the total fuel pressure difierential exceeds a value determined by the relative areas of piston 228 and valve 2I8, and also by the strength or spring 222, the spring is compressed and the valve opens.

When the inlet passage I82 is open, the pressure drops across valve 2I8 is less than the total fuel pressure differential by the amount of the pressure drop across restriction 2I2. Therefore, the force holding the valve 2I8 closed is smaller and consequently it opens at a lower value of fuel pressure differential than is the case when the inlet passage I82 is closed. 2

' Figure 18 There is illustrated in Figure 18 a jet system 248 which may be used in place of the jet systems shown in Figures 8 and 9, and which produces the same fuel-to-air ratio characteristics which are illustrated in Figure 8A.

In the. jet system 248, the restrictions I86, 282 and 2I2 are the same as the corresponding restrictions of Figure 9. The inlet and outlet passages are also the same and have been given corresponding reference characters. There is also provided in the jet system 248 a chamber 242 connected to the inlet chamber I84 by a restriotion 244 and connected to the inlet passage I82 by a restriction 246. Fuel may be discharged from the chamber 242 thru a restricted passage 248 controlled by a valve 258, which is biased to closed position by a spring 252.

When fuel inlet passage I82 is closed, fuel flows from inlet passage I88 either directly thru restriction I86 to outlet passage I88 or thru re- 8 striction 244, chamber 242, restriction 246, restriction 282, chamber HM, and restriction 2| 2 to outlet passage I88. Under these conditions, the pressure drop which acts on valve 258 in an 'opening direction is a predetermined proportion of the total pressure diiferential. This proportion was established by the relative areas of the restrictions 244, 248, 282 and 2I2,

When the inlet passage I82 is open, both restrictions 244 and 249 serve as inlets to the chamber 242, thereby increasing the pressure in that chamber and increasing the proportionality between the pressure drop across valve 258 and the total fuel pressure difierential. The valve 258 is then opened at a smaller value of fuel pressure differential than in the previous case.

Figure 11 The jet system 288 illustrated in Figure 11 'includes restrictions I88, 2I2 and 282, which are substantially the same as the corresponding restrictions of Figure 10. In Figure 11, the inlet passage I80 sll'iplieS fuel directly to a restriction 262. The restriction 262 opens into a chamber 264. The chamber 264 is connected thru a. restriction 286 to the inlet passage I82. A check valve 268 closes the restriction 266 whenever the pressurein chamber 264 is higher than that in inlet passage I 82. A restrictedpassage 210 leads from chamber 264 into chamber I9I. The passage 210 is controlled by a. valve 212 biased'to closed position by a spring 214.

When the inlet passage I82 is closed, the check valve 268 closes restriction 266, and the pressure drop acting in an opening direction'on valve 212 is some predetermined proportion of the total fuel pressure differential which is establshed bv the relative magnitudes of restrictions 282 ard I86. When the inlet passage I82 is also up n, the check valve 268 opens and increases the pressure in chamber 264, while the pressure on the downstream side of valve 212 remains substantially the same; Therefore, the pressure drop across the valve- 212 is now a greaer proportion of the total fuel pressure differential than was the case previously and, therefore, the valve 212 opens at a lower value of thetotal fuel pressure differential.

Figure 12 There is shown in Figure 12 a mixtu e control valve mechanism 300 and a jet system 302, which may be used in place of the corresponding ele- 304 which controls ports leading to inlet passages III, 306, 308 and 3I0. When the disc 334 is in its "rich position, shown in full lines in the drawing, the three inlet passages 306, .308 and 3I0 are all open. When'the valve 304 is in'its lean position, shown in dotted lines in the drawing, the inlet passages 306 and III are open,

greater proportion of the total pressure difierential across the jet system than was the case when only the inlet passages 306 and III were open. Therefore, the valve 320 opens at a lower value of fuel pressure differential.

Figure 13 There is shown in Figure 13 a mixture control valve mechanism 330 and a jet system 332, yvhich may be used in place of the mixture control and jet system of Figure 1. In the jet system of Figure 13, the restrictions I86 and 2I2 correspond to the same restrictions in the previous figure.

The mixture control valve mechanism 330 includes a valve 332 attached to a shaft 334. When the 'valve 332 is in its "rich" position, shown in full lines in the drawing, two 'inlet passages 336 and 338 are open. When the valve 332 is in its lean position. shown in dotted lines in the drawing, two inlet rassages 340 and342 are open. The inlet passage 336 leads thru a' restrictit-n 344 into a chamber 346, and the inlet passage- The pressuredrt-p thru the passage 356 acts on In the jet system 302, the jets or restrictions I86, 202 and 2I2, and the chamber I9I, function in the same manner as the corresponding elements of Figure 9. Fuel entering the jet system thru the inlet passage 306 passes thru a. fixed restriction 3I2 into a chamber 3I4. Fuel entering the jet system thru the inlet passage 303 passes thru a fixed restriction 3I6 into the chamber 3I4. Fuel entering the jet system thru the inlet passage 3I0 passes thru the fixed restriction 202 into the chamber I9I. A'restricted passage 3I8 connects the chambers 3| 4 and I9I, and is controlled by a valve 320 biased to closed position by a spring 322 and movable to open position by the pressure drop across the passage 3I3.

When the mixture control 300 is in its lean position, the inlet passages 308 and 3I0 enclosed, and the pressure in chamber I9! is substantially the same as the outlet pressure of the jet system. The pressure drop across passage 3I8 is then determined by the, relative sizes of the restrictions 3I2 and I86. When the mixture control is in'its rich position, the inlet passage 338 leading thru restriction 3 I 6 is open and the pres across valve 353 is a certain predetermined 'pr0-' portion of the total fuel pressure difierential, de-

pending upon the relative sizes of restrictions 354 and I86. When the mixture control is in its rich position, the chamber 346 is fed thru the relatively large restriction 344, and the pressure in chamber 346 is, therefore, higher. Consequently, the pressure drop across valve 358 is now a greater proportion of the total fuel pressure differential than before, and the valve 358, therefore, opens at a lower value of the total pressure differential.

Figure 14 There is shown in Figure 14 a jet system 380, which may be used in place of the jet system 60 of Figure 1. The mixture control valve mechanism I15 of Figure 7 should be used with the jet system of Figure 14. The jet system of Figure I4 is similar to that of Figure 1 except that the restriction I30 and its associated control mechanism has been omitted and additional control mechanism is provided for the enrichment valve H8 in the restriction II6. This additional control mechanism consists of a chamber 382 formed between a diaphragm 384 and a cover 383 which is attached by any suitable means to the jet system. The chamber 382 is connected to the inlet passage I30 thru a branch passage 388 having the restriction 330 in it. The chamber 382 is connected to the inner passage I82 by branch passage 392 having a. restriction 334 in it. A spring 396 biases the diaphragm 384 in a direction so that it tends to engage the end of the stem 338 of valve I I8.

When the mixture control is in its lean position. fuel'may flow from inlet passage I thru iii passage ilt, restriction 39d, chamber 382, restric tion 395, branch passage 392, restriction i22, chamber Edi, and restriction 82 5 to outlet passage 588. *The passage drop across diaphragm 38 i acts in a direction to compress spring 3% and to maintain diaphragm sec free of the end of valve stem 3%. The particular value of total pressure differential at which valve H8 opens is then determined by the area of valve i is and the strength of spring i2t.

:When the mixture control is in its rich" position, both inlet passages I80 and itli are open, and fuel may then enter chamber 382 thru either restriction 398 or 3%. The pressure in chamber 392 is then substantially equal to the pressure in the inlet passages Edd and i82. There is then no pressure'drop across the diaphragm set and the spring 3% moves the diaphragm 38% downwardly until it engages the end of valve stem 3%. The force of spring idil tending to hold valve lit closed is then partially opposed by the force of spring 395 tending to open it. Therefore, it takes asmaller value of total pressure differential to open valve t id and enrich the fuel flow.

"While I have shown and described certain preferred embodiments of my invention, other modifications thereof will readily occurto those skilled in the art, and I therefore intend my invention to be limited only by the appended claims.

I claim as my invention: I

1. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of interconnected passages and restrictions in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a chamber in said jet system, a passage including at least one of said restrictions connecting said chamber and said fuel conduit at one side of said jet system, second and third restrictions in parallel connectingsaid chamber and said fuel conduit at the other side of said jet system, a valve subject to the pressure in said chamber and adapted to be moved in an opening direction by said pressure for controllin one of said three restrictions, means biasing said valve to closed position, and valve means selectively movable between a first position wherein only one of said two parallel restrictions is open and a first predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established and a second position wherein both said parallel restrictions are open and a second predetermined relationship between said fuel pressure differential and the iuel flow thru said conduit is established, said valve means being efiective to vary the relationship between said pressure difierential and the pressure in said chamber so thatwhen said valve means is in said first position said valve opens when said fuel -pressure differential exceeds a first predetermined value, and when said valve means is in said second position said valve opens when said fuel pressure difierential exceeds a second predetermined value lower than said first predetermined value.

2. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of passages and restrictions in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a chamber in said let selectively movable between a first, position wherein only one of said two parallel restrictions is open and a first predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established and a second position wherein both said parallel restrictions are open and a second predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established, said valve means being effective to vary the relationship between said fuel pressure differential and the pressure diiferential which operates said valve so that when said valve means is in said first and second positions, said valve opens said one restriction when said fuel pressure differential exceeds first and second predetermined values, respectively,

3. A fuel supply system for an internal combustion engine, comprisinga conduit for fuel flowing to said engine, a plurality of parallel restricted passages in said conduit for regulating the fiow of fuel therethru in accordance with the fuel pressure differential across said passages. means for varying said fuel pressure diiferential. manually operable valve means for selectively opening said passages to the flow of fuel and movable betweenfa first position wherein a first of said passages is open and a first predetermined value is established for the total cross-sectional area of the open passages and a second position wherein said first passage and a secondpassage are open and a second predetermined value greater than said first predetermined value is established for said total cross-sectional area, first means to increase said total cross-sectional area when said valve means is in said first position and said pressure differential exceeds a first predetermined value, second means to increase said total cross-sectional area when said valve means is in said second position and said pressure difierential exceeds a second predetermined value lower than said first predetermined value, a third passage controlled by said manually operable valve means and opened thereby when said valve means is in said first position, a valve in said third passage and subject to said pressure diiferential acting thereon in an opening direction, a spring biasing said valve to closed position and eifective to maintain said valve closed until said pressure differential exceeds a third predetermined value higher than said first and second predetermined values, said valve being effective when said manually operable valve means is in said first position andsaid pressure diiferential'exceeds a fourth predetermined value greater than said third to increase said total area to an amount substantially equal to that obtained when said manually operable valve means is in said second position and said pressure differential exceeds said fourth predetermined value.

4. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of metering restrictions in said conduit v 13 a r for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a chamber in said jet system, at least one restricted passage connecting said flowing to said engine, a. jet system including a I plurality of metering restrictions in said conduit chamber and said fuel conduit at one side of said jet system, second and third restricted passages in parallel connecting said chamber and said fuel conduit at the other side of said Jet system, a valve responsive to the pressure differential across one of said three restricted passages for controlling the fuel flow therethru means biasing said valve to closed position,. valve means selectively movable between a first position wherein only one of said two parallel restricted passages is open and a first predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established and a second position wherein bothsaid parallel restricted passages are open and a second predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established whereby a greater fuel flow is produced by a given pressure differential, said pressure responsive valve being effective when said valve means is in said first position to open said one restricted passage and increase the fuel flow produced by a 'given pressure differential i value lower than said first predetermined value,

and means effective when said valve means is in either of saidfirst or second positions and sad pressure differential exceeds a third value greater than said first and second values to produce a predetermined fuel flow.

5. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of metering restrictions in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a chamber in said jet system,- at least one restricted passage connecting said chamber and said fuel conduit at one side of said jet system, second and third restricted passages in parallel connecting said chamber and said fuel conduit at the other side of said jet system, a valve responsive to the pressure differential across said one restricted passage for controlling the fuel flow therethru, means biasing said valve to closed position, a fourth passage connecting the opposite sides of said jet system and including a fixed restriction, a fifth passage connecting the opposite sides of said jet system, a valve in said fifth passage subject to said fuel pressure differential acting thereon in an opening direction, a spring biasing said last-mentioned valve' to closed position, and valve means selectively movable between a first position wherein said fifth passage and one of said two parallel restricted passages is open and a first predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established and a, second position wherein said fourth passage and. both said parallel restricted passages are open and. a second predetermined relationship between said fuel pressure diflerential and the fuel flow thru said conduit is established.

6. A fuel supply system for an internal combustion engine, comprising a conduit for fuel for regulating the flow of fuel therethru in accordance with the fuel pressure difierential across said jet system, means for varying 'said fuel pressure differential, a chamber in said Jet system, at least one restricted passage connecting said chamber and said fuel conduit at one side of said jet system, second and third passages including restrictions of different sizes connected in parallel between said chamber and said fuel conduit at the other side of said jet system, a valve responsive to the pressure differential across said one restricted passage for controlling the fuel flow therethru, means biasing said valve to closed position, fourth and fifth passages connected in parallel between the opposite sides of said jet system and including restrictions bf different sizes, and valve means selectively movable between a first postion wherein the one of said second and third passages having the larger restriction and the one of said fourth and fifth passages having the smaller restriction are open and a first predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established and a second position wherein the one of said second and third passages having the smaller restriction and the one of said fourth and fifth passages having the larger restriction are open and a second predetermined relationship between said fuel pressure differential and the fuel flow thru said conduit is established.

7-. A fuel supply'system for an internal combustion engine, comprising a conduit for fuel flowing to said e Inc, a jet system including a plurality of metering restrictions in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a first passage extending thru sai et system and including two restrictions in series, a second passage extending thru said jet system and including two restrictions in series, a third passage extending from the upstream side of said jet system to said first passage at a point between the two restrictions therein and including a single restriction, a branch passage connecting said point in said first passage with a point in said second passage between the two restrictions therein, a valve in said branch passage movable in an opening direction by the pressure drop between the ends of said branch passage, a

spring biasing said valve to closed position and effective to maintain said valve closed until said pressure drop exceeds a predetermined value and valve means for controlling the inlets to said first, second and third passages and selec ively movabfe between aflrst position wherein only the inlet of said first passage is open, thereby establ shing a first proportional relationship between said fuel pressure differential and said pressure drop, and a second position wherein the inlets of said first, second and third passages are all open, thereby establishing a. second proportional relationship between said fuel pressure differential and said pressure drop, said pressure responsive valve being effective due to the difference in said relationships when said valve means is in said first and second positions to open said branch passage and increase the total fuel flow when said fuel pressure differential exceeds first and second predetermined values, respectively.

8. A fuel supply system for an internal combustion engine. comprising a conduit for fuel flowing to said engine, a jet system including a is? plurality of metering restrictions in said conduit for regulating the flow of fuel therethru inaccordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, a first passage extending thru said jet system and including a single restriction, a second passage extending thru said jet system and including two restrictions in se- .ries, a chamber in said jet system, a first branch passage of limited capacity connecting said chamber and said first passage at the upstream side of the restriction therein, a second branch passage of limited capacity connecting said chamber and said second passage on the upstream side of the two restrictions therein, a third passage for delivering fuel into said second passage at a point between the two restrictions therein, a valve in said third passage movable in an opening direction by the-pressure in said chamber, a spring biasing said valve to closed position, and valve means for controlling the inlets to said first and second passages and selectively movable between a first position wherein only the inlet of said first passage is open so that only said first branch passage acts as an inlet to said chamber, and a second position wherein the inlets of both said first and second passages are open so that both said first and second branch passages act as inlets to said chamber, said pressure re-' sponsive valve being effective due to the difierence in the pressure in said chamber when said valve means is in said first and second positions to open said third passage and increase the total fuel flow when said fuel pressure differential exceeds first and second predetermined values, respectively.

9. A fuel supply system for an internal cornbustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of interconnected passages and restrictions in said conduit for regulating the flow of fuel therethru in accordancewith the fuelpressure differential across said jet system, means for varying said fuel pressure difierential, first and second fuel inlet passages opening into said let system from said conduit, a chamber in said jet system, a first one of said restrictions connecting said chamber and said first fuel inlet passage, a second of said restrictions connecting said chamber and said second fuel inlet passage, a third passage for delivering fuel to the outlet of said jet system. a valve in said third passage movable in an opening direction by the pressure in said chamber, a spring biasing said valve to closed position, and valve means for controlling said first and second fuel inlet passages and selectively movable between a first position wherein only said first inlet passage is open so that only said first restriction acts as an inlet to said chamber, and a second position wherein both said first and second fuel inlet passages are open so that both said first and second restrictions act as inlets to said chamber, said pressure responsive valve being effective due to the difference in the pressure in said chamber when said valve means is in said first and second positions to open said third passage and increase the total fuel flow when said fuel pressure differential exceeds first and second predetermined values, respectively.

10. A fuel supply systemfor an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of interconnected passages and restrictions in said conduit for regulating the flow of aesaave id fuel therethru in accordance with the fuel pressure'diiierential across said jet system, means for varying said fuel pressure differential, first and second fuel inlet passages opening into said g jet system from said conduit, an expansible chamber in said jet system having a movable wall, a first one of said restrictions connecting said chamber and said first fuel inlet passage, a I

second of said restrictions connecting said chamber and said second fuel inlet passage, a third passage for delivering fuel to the outlet of said jet system, a valve in said third passage, a spring valve opening means being effective due to the difference in the pressure in said chamber when said valve means is in said first and second positions to open said third passage and increase the total fuel flow when said fuel pressure differential exceeds first and second predetermined values, respectively.

ii. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a jet system including a plurality of interconnected passages and restrictions in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying said fuel pressure differential, first and second fuel inlet passages opening into sai jet system, a first one of said restrictions connecting said chamber and said first fuel inlet passage, a second of said restrictions connecting said chamber and said second fuel inlet passage, a third passage including third and fourth restrictions in series connecting said second fuel inlet passage to the outlet of said jet system, a fourth passage for delivering fuel into said third passage at a point between said third and fourth 5 restrictions, a valve in said fourth passage movable in an opening direction by the pressure in said chamber, a spring biasing said valve to closed position, and valve means for controlling said first and second fuel inlet passages and selec- 5 tively movable between a first position wherein only said first inlet passage is open so that only said first restriction acts as an inlet to said chamber, and a second position wherein both said first and second fuel inlet passages are open my so that both saidfirst and second restrictions act as inlets to said chamber, said pressure responsive valve being effective due to the difference in the pressure. in said chamber when said valve means is in said first and second positions to 65 open said third passage and increase the total fuel flow when said fuel pressure difierential ex-.

predetermined values, re-

jet system from said conduit, a chamber in said I 17 manually operable valve means for selectively opening said passages to flow of fuel and movable between a first position wherein a first of said passages is open and a first predetermined value is established for the total cross-sectional area of the open passages and a second position wherein said first passage and a second passage are open and a second predetermined value greater than said first predetermined value is established for said total cross-sectional area, means to increase said total cross-sectional area .when said valve means is in either of said first and second positions and said pressure differential exceeds a first predetermined value, a third passage controlled by said manually operable valve means and opened thereby when said valve means is in said first position, a valve in said third passage andsubject to said pressure differential acting thereon in an opening direction, a spring biasing said valve to closed position and effective to maintain said valve closed until said pressure differential exceeds a second predetermined value higher than said first predetermined value, said valve being effective when said manually operable valve means is in said first position and said ,pressure differential exceeds a third predeter- I said valve closed until said pressuredifferential exceeds a second predetermined value higher than said first predetermined value, said valve and said manually operable valve means cooperating to control said third passage so that when said manually operable valve means is in saidfirst position and said pressure differential mined value greater than said second to increase said total area to an amount substantially equal to that obtained when said manually operable valve means is in said second position and said pressure differential exceeds said third predetermined value.

13. A fuel supply system for an internal combustion engine, comprising a conduit for fuel flowing to said engine, a plurality of parallel restricted passages in said conduit for regulating the flow of fuel therethru in accordance with the fuel pressure differential across said passages, means for varying said fuel pressure differential, manually operable valve means for selectively opening said passages to the flow of fuel and movable between a first position wherein a first of said passages is open and a first predetermined value is established for the total cross-sectional area of the open passages and a second position whereinsaid first passage and a second passage are open and a second predetermined value greater than said first predetermined value is established forsaid total cross-sectional area, means to increase said total cross-sectional area when said valve means is in either of said first and second positions and said pressure differential exceeds a first predetermined value, a third passage, a valve in said third passage and subject to said pressure differential acting thereon in an opening direction, a spring biasing said valve to closed position and effective to maintain exceeds a third predetermined value greater than said second said total area is increased to an amount substantially equal to that obtained when said manually operable valve means is in 1 said second position and said pressure differential exceeds said third predetermined value.

14. A fuel supply system for an internal combustion engine, comprising a conduitfor fuel flowing to said engine, a jet system including a plurality of interconnected passages and restrictions in said conduit for regulating the fiow of fuel therethru in accordance with the fuel pressure differential across said jet system, means for varying saidfuel pressure differential, first and second fuel inlet passages opening into said jet system from said conduit, a chamber in said jet system, a first one of said restrictions connecting said chamber and said first fuel inlet. passage, means connecting said'chamber and said second fuel inlet passage, a third passage for delivering fuel to the outlet of said jet system, a valve in said third passage movable in an opening direction by the pressure in said chamber, aspring biasing said valve to closed position, and valve means for controlling said first and second fuel 'inlet passages and selectively movable between a first position wherein only said first inlet passage is open so that only said first restriction acts as an inlet to said chamber, and a second position wherein both said first and second fuel inlet passages are open so that both said first restriction and said connecting means act as inlets to said chamber, said pressure responsive valve being effective due to the difference in the pressure in said chamber when said valve means is in said first and second positions-to open said third passage and increase the total fuel flow when said fuel pressure difi'erential exceeds first and second predetermined values, respectively.

JQHN M. BARR.

' REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS 

